Method of masking metal sheets and the like



Patented Apr. 14, 1942.

meme

METHOD'OF MASKINGMETAL SHEETS AND I rename Ferdinand W. Humphner, Oak Park, Ill'., assignorto Mid-States Gummed Paper 60., Chicago, 111.,

a corporation.- 02 Delaware Noni-swing. Application dune 23, 1939,.

SerialNo. 280,891

7 Claims.

This invention relates to a protective backing for metal sheets and the like and tothe method of masking such sheets with a protective backing. In, the manufacture of highly polished metal articles made from metal stampings and other Similar forms of converting metal objects, as well as-other products similar to metal in smoothness, etc., it is. desirable to protect .the finish from scratches and other markings during the process of manufacture. There are other materials, such as Bakelite, etc., having smooth surfaces which it is important to protect from scratches during forming operations. The more common practice in recent years has been to apply to the metal or other surface a, tape or like strip.,consisting of treated paper with a pressure-sensitive rubber base adhesive. The paper is often creped so as to make'it repellent to the rubber base. Sometimes it is treated so as to render the fibers rrepellent to the rubber adhesive. The product is expensive and subject to deterioration. The rubber compound does not keep its original qualities permanently and becomes unstabilized due to layer thereon, or, if desired: the sheet may be used without such processing.

The tape 'just described provided with the animal glue will remain in. its original state for long periods of time. Since it is dry, and not adhesive, it can be rolled, stacked, or handled in any desired way.

When it is desired to apply the sheets to metal, I remoisten the gummed sheet with asolution of water and formaldehyde. To 'this is preferably added glycerin or some suitable like material. Also, I find that the product is' improved by adding a wetting out reagent, such as a sulphonated higher alcohol, an' example of which may be Aerosol.

' In addition to moistening' the gummed; side of the sheet, I find it very desirable to moistenboth vide an inexpensive product which does not deteriorate and which may be handledsimply and removed from the surface as desired. A further object is to provide a method and product wheresure-sensitive adhesive'tape applicable to metal surfaces and the like to which ordinary gummed tape may not be satisfactorily applied. Other specific objects and advantages will appear as the specification proceeds.

In the practice of my invention, any suitable kraft paper, cloth, or other material may serve as a base, and no special processing is required for its'protection before the application of adhesive. To this base is applied acoating of animai glue which may be from bone or hide extraction, or other like adhesive. 'I prefer a jell strength of 60 grams and upwards. The glue is mixed with equalparts of water, and then applied 'to the base by any suitable means for producing a gummed sheet.- If the paper is to be used in largesheets, it mayibedesirable'to processthe sheet to remove the curl, fracturing the gum sides with the same solution, the solution pro viding a lubricant on lthe side opposite the adhesive side. The lubricating .and wetting quality of the lubricant on the ungummed side aids in enabling the paper to stretch under die stamping operations and also in rendering'the paper pliable to make it adhere more readily to the metal surface.

The metal sheets may be stored until ready to use, either with or withoutthe paper backing, and the paper backing may be removed by peeling off the strip or sheet which has been rendered pressure-sensitive by the action of the solution. V A

e The formaldehyde acts as a tanning or insolubilizing agent with respect to the gelatin or-animal glue, causing it to become pressure-sensitive in action. Theglycerin, acting as a plasticizer. cooperates with the formaldehyde in preventing complete insolubilizing of the glue and in main taining it in a plastic and pressure-sensitive adhesive condition.

It will be understood that the solution may be varied by those skilled in the art by the substitution of equivalents. For example, glycerin may be replaced with products suchas sulphonated oils, ethylene glycol, or any other organic compounds of the same general class asglycerin. Formaldehydeomay be replaced with trioxymethylene, potassium dichromate, calcium chromate, tannin, etc. The quantities and proportions' us'ed may be varied widely to suit conditions, the thickness of the glue coating, and the backing material used. Those skilled in the art will readily understand the proportions desired.

sheets and to which an ordinary g'ummed tape cannot satisfactorily be applied arid-readilyreleaving a clean metal surface.

While'in the foregoing description, I have set forth certain details, and certain steps in sequence, it will be understood that such details in structure and steps of operations may be readily" varied by those skilled in the art without departing from the spirit of my invention.

I wish it to be understood that I do not desire to be limited to the exact details of construction shownand described, for obvious modifications will occur to a person skilled in the art.

I claim: 1

1. The method of removably masking a metal surface and the like, comprising applying to. the surface of a tape a liquid coating of glue, drying the glue to produce a dry gummed tape, thereafter moistening the dry glue surface of the tape with a solvent therefor containing an agent capable of tanning said glue and a plasticizing agent, and applying the moistened glue surface of the tape to said metal surface.

2. The method of removably masking a metal surfa'ce and the like, comprising applying to the surface of a tape a liquid coating of animal glue,

- drying the glue to produce a dry gummed tape,

thereafter moistening the dry glue surface of the tape with a solvent therefor containing formalde-f hyde and, glycerin, and applying the moistened glue surface of the tape to said metal surface.

3. The method of removably masking a metal surface and the like'with adhesive sheetmate rial having alayer of dry animal glue on one moved. The present product has the characterisside, comprising wetting the dry glue with a water solution containing a tanning agent and a plasticizing agent, wetting also .the other side of said sheet material with said solution', and applying the moistened material to said metal surface.

4. The method of removably masking a metal surface and the like comprising wetting a tape 1 provided with a layer of dry animal glue with water containing formaldehyde and glycerin, and applying the moistened tape to said surface.

5. In a process for removably masking a metal surface and the like, the steps of wetting a tape surfaced with dry animal glue with water containing a tanning agent for said glue, and applying the moistened tape to said surface. 1

6. The method of protecting a metal surface and thelike, comprising wetting a tape having a layer of dry'glue thereon withan aqueous solution containing a tanning agent for said glue and a plasticizing agent, applying the moistened tape to said surface, and after the protection of said surface has been served pulling the tape together with its moist glue layer from said surface.

7. A masked-surface comprising a tape base material and a layerof glue having its one surface adhesively secured to said base material, said glue being treated with a tanning agent, and glycerin on the other surface of said layer of glue and extending only partially through said layer, said other surface of the glue layer being in contact with the masked surface, the portion of said layer adjacent the surface which is secured to said base material being substantially dry whereby said layer is caused to break away from the surface which is masked and cling to said base when the base is pulled from the masked surface. v

FERDINAND W. HUMPHNER. 

